1. Field of the Invention
The present invention relates to a liquid crystal display apparatus and, more particularly, to a liquid crystal display apparatus having a simple arrangement for effectively preventing the temperature of its liquid crystal panel and polarizers from rising.
2. Description of the Related Art
In recent years, a liquid crystal display apparatus which offers as good display quality as CRT display apparatus have been put to practice. Liquid crystal display apparatus, in general, have advantages over CRT display apparatus in terms of their thinness and energy-saving nature. However, such a liquid crystal display apparatus tends to exhibit lowered display performance due to deterioration of its polarizers and liquid crystal display panel (LCD) which is caused when the temperature of its liquid crystal display sections rises.
There has been proposed the art of cooling a liquid crystal display apparatus with use of cooling means to suppress a temperature rise at liquid crystal display sections during their operation. Generally, such cooling is achieved by taking in ambient air present around the liquid crystal display apparatus. This provides a substantial cooling effect but raises a problem that dust adheres to the liquid crystal panel to affect an image displayed. Though there has been proposed a liquid cooling method that is free from such a problem caused by dust in which a liquid crystal panel and polarizers are attached to a cooling container having a coolant circulating therein, this method involves such problems as contortion of a displayed image due to the difference in refraction index between the coolant and air.
The construction of a conventional liquid crystal display apparatus is schematically shown in FIG. 12. As shown, a section having liquid crystal panels 6R, 6G and 6B and polarizers 5R, 5G, 5B, 7R, 7G and 7B accommodated within a hermetic container 13 is cooled by a cooling fan 11.
Since this art achieves cooling by circulating air within the hermetic container 13, a problem caused by dust is not raised. This liquid crystal display apparatus operates as follows.
Light emitted from a light source 1 becomes incident on a polarized beam splitter 2 and is split into P-polarized light and S-polarized light thereby. The P(S)-polarized light component outgoing from the polarized beam splitter 2 is further split into beams having respective wavelengths corresponding to three primary colors (red, green and blue) for which respective liquid crystal panels 6R, 6G and 6B are adapted by dichroic mirrors 3 and reflection mirrors 4. These beams are optically modulated by respective liquid crystal panels 6R, 6G and 6B, then become incident on a prism 8, pass through a projecting lens 9, and are enlargedly projected onto a screen.
Liquid crystal display sections for red, green and blue comprising the polarizers 5R, 5G and 5B on the incident side, the liquid crystal panels 6R, 6G and 6B, and polarizers 7R, 7G and 7B on the outgoing side are disposed within the hermetic container 13 and adapted to be air-cooled by the cooling fan 11.
In order for air from the cooling fan 11 to be efficiently sent to the liquid crystal panels 6R, 6G and 6B and the polarizers 5R, 5G, 5B, 7R, 7G and 7B, the display sections are respectively enclosed by ducts 18R, 18G and 18B each having a sectional area substantially equal to the size of a blowing port through which air flows toward the liquid crystal panels 6R, 6G and 6B and the polarizers 5R, 5G, 5B, 7R, 7G and 7B.
Other known approaches includes use of one axial flow fan for one liquid crystal display section as in a liquid crystal display apparatus described in Japanese Unexamined Patent Publication JP-A 6-194621 (1994), use of a multiblade fan, and use of a crossflow fan.
Further, the art of improving the cooling performance and preventing leakage of noise to the outside is known from Japanese Unexamined Patent Publication JP-A 9-113998 (1997), wherein liquid crystal panels and a cooling fan are disposed within a hermetic container of metal.
Such conventional liquid crystal display apparatus involves the following problems.
(1) The conventional apparatus are not designed to what extent the polarizers and liquid crystal panel for each color should be cooled. For instance, the liquid crystal display apparatus using a single axial flow fan has a difficulty in appropriately distributing a circulating air flow depending on the heat value of each liquid crystal panel and requires an air guide path or guider of an intricate configuration to utilize the total circulating air flow. Where such a guider is used in combination with an axial flow fan, peak noise is generated in proportion to the number of revolutions of the fan to make the total noise louder and harsh.
(2) Since an axial flow fan, even when fixed to either the bottom plate of the hermetic container or another member present in the container, sucks air from the periphery thereof and sends cooling air toward the liquid crystal module, it is necessary to provide a space between the axial flow fan and the bottom plate and, hence, noise generated by the axial flow fan and noise generated when air is sucked by the axial flow fan vibrate the bottom plate, with the result that the vibration propagates to the outside as noise. Such vibration can be reduced by taking measures such as making the bottom plate thicker. In this case, however, the bottom plate is entirely made thicker in spite of the fact that the vibration is generated from the space under the axial flow fan. This makes resin molding difficult and leads to an increase in cost.
(3) Use of a duct extending from the fan is proposed for efficiently directing circulating air to liquid crystal panels. This approach, however, cannot increase the flow velocity of air at a point where the temperature of the liquid crystal panels rises. Consequently, the amount of air to be circulated needs to be augmented, or stated otherwise, it is difficult to decrease the cooling air flow, hence, difficult to achieve efficient cooling.
(4) The arrangement where each liquid crystal display section is provided with a cooling fan in a one-to-one relationship makes the whole apparatus intricate and larger in size while leading to increased cost.
The invention is made to solve the problems, and an object is to provide a liquid crystal display apparatus in which liquid crystal panels and polarizers can be effectively cooled by a simple arrangement.
The invention provides a liquid crystal display apparatus comprising a light source, a hermetic container, and liquid crystal display sections for red, green and blue, respectively, disposed within the hermetic container, the liquid crystal display sections each having a liquid crystal panel and a polarizer, wherein light emitted from the light source is enlarged and projected, the liquid crystal display apparatus further comprising a first blower for sending cooling air to the liquid crystal display section for blue, and a second blower for sending cooling air to the liquid crystal display sections for red and green, the first and second blowers being disposed within the hermetic container.
In one feature of the liquid crystal display apparatus, the first and second blowers comprise a multiblade fan and an axial flow fan, respectively.
In another feature of the liquid crystal display apparatus, the first and second blowers each comprise an axial flow fan, and the second fan is adapted to send cooling air to one of the liquid crystal display section for red and the liquid crystal display section for green and then to the other liquid crystal display section.
In yet another feature of the liquid crystal display apparatus, one of the first and second fans comprises an axial flow fan which is spaced apart from the hermetic container, and a reinforcing member is provided in a portion of the hermetic container which portion is opposite to the axial flow fan.
In yet another feature of the liquid crystal display apparatus, a side plate is provided between the liquid crystal panel and the polarizer of each of the liquid crystal display sections for respective colors to be placed outside an image displaying portion of the liquid crystal panel and be perpendicular to the polarizer.
The invention also provides a liquid crystal display apparatus comprising a light source, a hermetic container, liquid crystal display sections for red, green and blue, respectively, disposed within the hermetic container, the liquid crystal display sections each having a liquid crystal panel and a polarizer, wherein light emitted from the light source is enlarged and projected, the liquid crystal display apparatus further comprising blowing means for sending cooling air to the liquid crystal display sections for red, green and blue at a ratio of approximately 1:1:4, respectively.
According to the invention, the combinations of polarizers and liquid crystal panels corresponding to red, green and blue are disposed within the hermetic container to prevent dust from adhering to any liquid crystal display section, and the polarizers and the liquid crystal panels can be efficiently cooled.
Further, generation of noise can be suppressed.